Porous nanoparticles produced by solvent-free emulsification

ABSTRACT

Disclosed herein are porous nanoparticles having a particle size of from about 50 nm to about 2 μm and a pore diameter of from about 20 nm to about 400 nm. The porous nanoparticles include a resin composition comprising at least one polyester resin in the absence of an organic solvent, and a surfactant.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of, and claims the benefit of priorityto, U.S. patent application Ser. No. 13/740,314, filed Jan. 14, 2013,the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to porous nanoparticles and methods ofproducing the porous nanoparticles.

BACKGROUND

Materials of high surface area and porosity have found great utility ina range of industries including, for example, the automotive, cosmetic,coatings, and chemical industries. For instance, in the automotiveindustry, porous materials are currently being researched to lighten carparts, reduce material costs, and improve fuel efficiency. In thecosmetic industry, porous particles may be used as delivery vehicles foroils and other cosmetics, allowing these materials to be handled as apowder rather than a paste. In the coatings industry, porous materialsor films may be used to reduce the amount of resin used in covering asurface, or such materials may be used in producing a paint that isporous (breathable) for moisture transmission and control. In thechemical industry, nanoporous materials may be used for gas adsorption,filtration and chromatography.

Various methods have been developed for the production of porousmaterials of small size. However, few approaches have been developed forthe production of porous nanosize particles from polymeric materials.One conventional process involves producing core shell particles, butthe approaches used to produce these hollow micron-sized spheres are notpractical on a large scale and make use of complicated phase inversionchemistries, step-by-step assemblies, or microfluidics.

A new mechanism or chemistry that would produce porous nanoparticles bya simplified manufacturing process would therefore be desirable.

SUMMARY

Disclosed herein is a process for manufacturing porous nanoparticles. Insome embodiments, the process includes adding a first aqueous solutioncontaining a surfactant to a resin composition containing at least oneresin to form a water-in-oil emulsion. A second aqueous solutioncontaining deionized water may be added to the water-in-oil emulsionprior to phase inversion to form a water-in-oil-in-water double emulsioncomprising porous nanoparticles, and porous nanoparticles may berecovered from the double emulsion. The porous nanoparticles may have aparticle size of from about 50 nm to about 2 μm and a pore diameter offrom about 20 nm to about 400 nm.

Also provided is a continuous process for producing porous nanoparticleswhich, in some embodiments, involves continuously adding a resincomposition comprising at least one resin to a feed section of the screwextruder. A first aqueous solution containing a surfactant may be addedto the resin composition to form a water-in-oil emulsion, and a secondaqueous solution containing deionized water may be added to thewater-in-oil emulsion prior to phase inversion to form awater-in-oil-in-water double emulsion comprising porous nanoparticles.In embodiments, porous nanoparticles may be recovered from the doubleemulsion.

Further provided are porous nanoparticles containing at least onepolyester resin in the absence of an organic solvent, and a surfactant.The porous nanoparticles may have a particle size of from about 50 nm toabout 2 μm and a pore diameter of from about 20 nm to about 400 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an exemplary screw extrusion devicethat may be employed in the processes of the present disclosure.

FIG. 2A is an SEM image of the porous nanoparticles produced in Example1 at ×40.0 k magnification. FIG. 2B is an SEM image of the porousnanoparticles produced in Example 1 at ×60 k magnification.

FIG. 3A is an SEM image of the porous nanoparticles produced in Example2 at ×20.0 k magnification. FIG. 3B is an SEM image of the porousnanoparticles produced in Example 2 at ×10.0 k magnification.

FIG. 4A is an SEM image of the porous nanoparticles produced in Example3 at ×20.0 k magnification. FIG. 4B is an SEM image of the porousnanoparticles produced in Example 3 at ×10.0 k magnification.

FIG. 5A is an SEM image of the porous nanoparticles produced in Example4 at ×20.0 k magnification. FIG. 5B is an SEM image of the porousnanoparticles produced in Example 4 at ×10.0 k magnification.

EMBODIMENTS

This disclosure is not limited to particular embodiments describedherein, and some components and processes may be varied by one of skill,based on this disclosure. The terminology used herein is for the purposeof describing particular embodiments only, and is not intended to belimiting.

In this specification and the claims that follow, singular forms such as“a,” “an,” and “the” include plural forms unless the content clearlydictates otherwise. All ranges disclosed herein include, unlessspecifically indicated, all endpoints and intermediate values.

As used herein, the modifier, “about,” used in connection with aquantity is inclusive of the stated value and has the meaning dictatedby the context (for example, it includes at least the degree of errorassociated with the measurement of the particular quantity). When usedin the context of a range, the modifier, “about,” should also beconsidered as disclosing the range defined by the absolute values of thetwo endpoints. For example, the range, “from about 2 to about 4,” alsodiscloses the range, “from 2 to 4.”

The present disclosure provides processes for forming porousnanoparticles, such processes for forming porous nanoparticles in theabsence of an organic solvent. In embodiments, a process of the presentdisclosure includes utilizing an extruder, such as a twin-screwextruder, to carry out continuous phase inversion of a continuouspolymer phase into a flowable latex emulsion.

The term “emulsion” refers, for example, to a mixture of two or moreliquids in which one liquid (“dispersed phase”) is dispersed in a second(“continuous phase”). The phrase “continuous phase inversion” refers,for example, to a situation in which a substance initially comprisingthe continuous phase inverts to become the dispersed phase, and viceversa.

In embodiments, the processes for forming porous nanoparticles of thepresent disclosure may occur in the “absence of an organic solvent.” Thephrase in the “absence of an organic solvent” refers, for example, to aprocess in which the solutions and/or compositions utilized in theprocess are substantially free of organic solvents or free of organicsolvents. The phrase “substantially free of organic solvents” refers,for example, to a composition or solution where there are only minoramounts of organic solvents present and/or only a minor amount oforganic solvent has not been removed; such as, for example, less thanabout 2% by weight organic solvent is present in any composition and/orsolution utilized in the process, or from about 1% to about 0.001% byweight organic solvent is present in any composition and/or solutionutilized in the process. The term “free of organic solvents” refers, forexample, to a composition or solution where there are no organicsolvents are present and/or all organic solvents have been removed fromthe composition or solution. In specific embodiments, each of thecompositions and/or solutions used and/or added during the process offorming the porous nanoparticles of the present disclosures are eitherfree or substantially free of organic solvents.

For example, in embodiments, organic solvents may not be used todissolve the polyester resin for emulsification. However, minor amountsof organic solvents may be present in such resins as a consequence oftheir use in the production process of forming the polyester resin, butsuch solvents are not present in a sufficient amount to dissolve thepolyester resin for emulsification. The term “minor” refers, forexample, to trace amounts of organic solvents in the resin, such as, forexample, less than about 1% organic solvents, such as from about 1% toabout 0.001% organic solvents by weight relative to the total weight ofthe resin. In embodiments, amounts of organic solvents in the resin maybe less than about 0.1% organic solvents by weight relative to the totalweight of the resin.

In the methods of the present disclosure, continuous phase inversion ofa continuous polymer phase into a flowable latex emulsion may be carriedout with an extruder, such as a twin-screw extruder. In embodiments,forming porous nanoparticles in the absence of an organic solvent bycontinuous phase inversion of a continuous polymer phase into a flowablelatex emulsion may completely occur within the confines of one extruder,such as a twin-screw extruder. The porous nanoparticles formed in theabsence of an organic solvent by the continuous phase inversion processof the present disclosure may be used to produce porous nanoparticleshaving nanopores, such as nanopores having a diameter of less than about400 nm, such as pores having a diameter in the range of from about 20 nmto about 400 nm, or from about 25 nm to about 180 nm, or pores having adiameter in the range of from about 30 nm to about 100 nm, or poreshaving a diameter in the range of from about 40 nm to about 80 nm. Suchnanopores may have an average diameter in the range of from about 40 nmto about 100 nm, or about 50 nm to about 70 nm. In embodiments, theporous nanoparticles formed in the absence of an organic solvent by thecontinuous phase inversion process of the present disclosure may be usedto produce porous nanoparticles having cell walls with a cell wallthickness in the range of from about 5 nm to about 100 nm, such as acell wall thickness in the range of from about 10 nm to about 50 nm, ora cell wall thickness in the range of from about 15 nm to about 30 nm,or cell walls having an average cell wall thickness of from about 18 nmto about 22 nm, or of about 20 nm.

The methods of the present disclosure may include the addition of aresin, such as polyester, or an amorphous polyester, blended with abasic powder, such as NaOH powder, to the hopper of an extruder, such asa twin-screw extruder, by any suitable means, such as a gravimetricfeeder. The methods may also include adding surfactant solution to theresin. The surfactant solution may be added to the hopper with theresin, or it may be added at a section of the extruder downstream of thehopper. Additionally, deionized water may be added at multiple locationsalong the extruder, such as both directly after the surfactant solutionas well as further downstream. In embodiments, deionized water may alsobe added outside of the screw extruder.

The average residence time within the extruder may be tailored asdesired in order to achieve the desired porous nanoparticle size. Theterm “residence time” refers, for example, to the time that elapses inthe process from feeding the resin component to the extruder to theporous nanoparticles exiting the extruder. In embodiments, the averageresidence time within the extruder may be in the range of from about 1minute to about 2 hours, such as in the range of from about 2 minutes toabout 30 minutes, or in the range of from about 4 minutes to about 10minutes.

The nanoporous latex emulsion produced according to the processes of thepresent disclosure may have a particle size of from about 50 nm to about2 μm, such as from about 75 nm to about 1 μm, or from about 100 nm toabout 500 nm.

Continuous Process

In embodiments, the present disclosure provides a continuous process formanufacturing porous nanoparticles. The term “continuous” refers, forexample, to a process that may be performed without interruption, thatis, a process in which raw materials are continuously processed tocompleted products. While a continuous process may thus be conducted 24hours per day, 7 days per week, it is understood that the process may beperiodically stopped, such as for maintenance purposes.

Embodiments of the continuous process for producing porous nanoparticlesdisclosed herein may include continuously feeding components into a feedsection of a screw extruder. In embodiments, the process may comprisedry-blending at least one resin and a neutralizing agent in the absenceof a solvent to form a resin mixture. The term “dry-blending” refers,for example, to a mixing process (typically, a low-shear mixing process)in which ingredients are blended together to form a relativelyfree-flowing heterogeneous mixture of the ingredients in particulateform. The neutralizing agent may be present in a concentration of fromabout 0.1 ppH (parts per hundred) to about 3 ppH, such as from about 0.3to about 2 ppH, or from about 0.25 to about 1.0 ppH. Concentration ofthe components is provided rather than the rates to achieve the desiredcomposition, since flow and feed rates vary with the scale of theprocessing equipment.

In embodiments, a first aqueous solution comprising a surfactant may beadded to the resin mixture in the extruder. The first aqueous solutioncomprising a surfactant may be co-fed with the resin into the extruderfeed hopper, or the first aqueous solution may be added to the resinmixture in the extruder at a location along the extruder downstream fromthe feed section. The first aqueous solution comprising a surfactant maybe fed at a rate such that the surfactant is at a concentration of fromabout 2% by weight to about 15% by weight of the resin, such as fromabout 2.5% by weight to about 10% by weight of the resin, or from about3% by weight to about 8% by weight of the resin.

In embodiments, the neutralizing agent may be co-fed with the firstaqueous solution comprising surfactant. For example, in embodiments, adry-blended resin composition may be added at the feed section of theextruder, and then the neutralizing agent and the first aqueous solutioncomprising a surfactant may be co-fed at a section of the extruderdownstream from the feed section.

In embodiments, the first aqueous solution comprising a surfactant mayfurther contain at least one active compound or material, such as acosmetic, a chemical and/or a pharmaceutical. The term “active compound”refers for example to an agent, drug, compound, composition of matter ormixture thereof which provides some chemical, physiological,psychological, biological, or pharmacological, and often beneficial,effect when in the environment of use.

Suitable active compounds may include foods, food supplements,nutrients, drugs, antacids, vitamins, antibacterial agents, antifungalagents, antibiotics, anti-inflammatory agents, other compounds thatprovide a benefit in the environment of use. For example, activecompounds may include any physiologically or pharmacologically activesubstance that produces a localized or systemic effect or effects inanimals, such as mammals, for example, humans. Active compounds may alsoinclude any desired inorganic and organic compounds.

In embodiments, the active compounds may be selected from, for example,proteins, enzymes, enzyme inhibitors, hormones, polynucleotides,nucleoproteins, polysaccharides, glycoproteins, lipoproteins,polypeptides, steroids, hypnotics and sedatives, psychic energizers,tranquilizers, anticonvulsants, antidepressants, muscle relaxants,antiparkinson agents, analgesics, anti-inflammatories, antihistamines,local anesthetics, muscle contractants, antimicrobials, antimalarials,antivirals, antibiotics, antiobesity agents, hormonal agents includingcontraceptives, sympathomimetics, polypeptides and proteins capable ofeliciting physiological effects, diuretics, lipid regulating agents,antiandrogenic agents, antiparasitics, neoplastics, antineoplastics,antihyperglycemics, hypoglycemics, nutritional agents and supplements,growth supplements, fats, ophthalmics, antienteritis agents,electrolytes and diagnostic agents.

The at least one active compound or material may be present in anyeffective amount. In embodiments, the amount of active compounds presentin the porous particle may be tuned as desired, for example by varyingthe amount and/or timing of the addition of the active compound toarrive at the desired active compound content.

In embodiments, the active compound may be added at the same time (andoptionally mixed with) the surfactant solution. The amounts of activecompounds in the surfactant solution may vary depending on the desiredeffect and/or the desired amount of active compound to be included inthe porous particle. In embodiments where the at least one activecompound is added at the same time (and optionally mixed with) thesurfactant solution, the at least one active compound or material andthe surfactant may together comprise, for example, less than about 50percent by weight of the first aqueous solution, such as from about 10to about 45 percent by weight of the first aqueous solution, or fromabout 20 to about 40 percent by weight of the first aqueous solution.For example, in embodiments, the at least one active compound maycomprise from about 1 to about 40 percent by weight of the first aqueoussolution, such as from about 5 to about 30 percent by weight, or fromabout 10 to about 25 percent by weight of the first aqueous solution.

The addition of the first aqueous solution comprising a surfactant tothe resin composition may facilitate the production of a water-in-oilemulsion. That is to say, the surfactant solution may become emulsifiedand dispersed within the resin (continuous phase), forming awater-in-oil emulsion of the surfactant solution within the resin. Inembodiments, a second aqueous solution comprising deionized water may beadded to the emulsion at a location further downstream from the locationwhere the first aqueous solution comprising a surfactant is added. Thesecond aqueous solution comprising deionized water may be added beforephase inversion of the emulsion; for example, in embodiments, the secondaqueous solution comprising deionized water may be added directly afterthe first aqueous solution comprising a surfactant. Addition of thesecond aqueous solution comprising deionized water may be achieved viawater injection ports into the extruder.

In embodiments, the second aqueous solution may further comprise asurfactant. Including a surfactant in the second aqueous solutioncomprising deionized water may be used to promote pore formation at thesurface of the porous nanoparticles. For example, injecting a secondaqueous solution comprising deionized water and surfactant may, inembodiments, produce porous nanoparticles with an increased degree ofsurface porosity (as compared to internal porosity), such as a surfaceporosity of from about 10% to 60% of the surface of the nanoparticles,or from about 20% to about 50%, or from about 30% to about 40%. Surfaceporosity may also be increased by increasing the injection rate of thesecond aqueous solution comprising deionized water (not necessarilycomprising surfactant).

Phase inversion may occur following the addition of deionized water tothe water-in-oil emulsion of the resin mixture and surfactant, yieldinga double emulsion (that is, a water-in-oil-in-water emulsion) comprisingporous nanoparticles. For example, deionized water may be added to forma double emulsion with a solids content (by weight) of from about 5% toabout 75%, such as from about 10% to about 50%, or from about 20% toabout 40%. The term “double emulsion” refers, for example, to a colloidin which a first emulsion is dispersed within another liquid. The otherliquid may be a third liquid, or a second instance of the inner liquidof the first emulsion.

In embodiments, deionized water may be added at a second locationdownstream from the first deionized water addition location and/or afterthe double emulsion is collected from the extruder. For example, theextruder may discharge the emulsion into a stirred reactor, wheredeionized water may be added. Deionized water may be added in anyeffective amount to dilute the double emulsion comprising porousnanoparticles and increase flowability of the double emulsion.

The extruder may have segmented barrels and the temperature, as well asother process parameters, of each barrel section may be controlledindependently. For example, the heating and cooling of each barrel maybe controlled independently. The screw elements of the extruder may besegmented for ease of design and to meet particular mixing dynamics atdifferent sections for particular reactions and proper dispersions, suchas neutralization reactions, water-in-oil dispersions, stabilization,and phase inversion to produce porous nanoparticles having a desiredparticle size and pore size, such as nanosized particles with nanoporousfeatures. The process disclosed herein may be used to producefully-formed porous nanoparticles with desired particle sizes that maybe collected from the extruder. As used herein, “fully formed” indicatesthat there are discrete polymer particles within a continuous aqueousmedium.

In embodiments, extrusion conditions such as temperature, screw speed,feed rate of mixture components may be adjusted to facilitate productionof porous nanoparticles. For instance, the screw speed varies dependingon the size of the extruder and may be at a rate of from about 50 rpm toabout 600 rpm, such as from about 100 rpm to about 500 rpm, or fromabout 200 rpm to about 300 rpm. For example, for an 18 mm extruder, thescrew speed may be from about 100 rpm to about 300 rpm. In embodiments,the temperature of each barrel may be from about 70° C. to about 200°C., such as from about 80° C. to about 180° C., or from about 85° C. toabout 175° C. In embodiments, the temperature of each barrel may varydepending on the zone within the extruder. For example, within a meltingzone, the temperature may be from about 65° C. to about 200° C., such asfrom about 75° C. to about 190° C., or from about 85° C. to about 175°C., and within a dispersion zone, the temperature may be from about 50°C. to about 150° C., such as from about 70° C. to about 140° C., or fromabout 80° C. to about 130° C.

The length/diameter (L/D) ratio of the extruder may be lengthened orshortened. In addition, mixing intensity, shear stress, and shear ratemay be adjusted by proper screw design to meet desired mixing dynamicsfor particular processes. For example, the mixing may be distributive,dispersive, dissipative, and/or chaotic. Fill volumes, local pressure,and feed rate, for example, may be controlled by varying screw speeds.

The time the components stay in the extruder may be lengthened orshortened to produce porous nanoparticles having a desired particle sizeand pore size. For example, in embodiments, the average residence timewithin the extruder may be in the range of from about 1 minute to about2 hours, such as in the range of from about 2 minutes to about 30minutes, or in the range of from about 4 minutes to about 10 minutes.When the extruder has segmented elements, the time the components stayin one segment may be lengthened or shortened.

In embodiments, the porous nanoparticles may be recovered from thewater-in-oil-in-water double emulsion. In embodiments, porousnanoparticles may be recovered from the double emulsion when it isdischarged from the screw extruder. Consequently, the above stepsproduce porous particles with desired particle size and pore size, suchas nanosized particles with nanoporous features.

In embodiments, the pores of the porous nanoparticles produced accordingto the instant disclosure may be loaded with a material apart from theresin matter. For example, the pores of the porous nanoparticles may bepartially or completely filled or loaded with an active compound ormaterial, such as a cosmetic, a chemical and/or a pharmaceutical. Inembodiments, such loaded particles may comprise at least one activecompound, such as a cosmetically or pharmaceutically active compound,where the at least one active compound is present inside the particles.Such active compounds may also be present at the surface of loadedparticles.

Particles may be loaded with an active material by any suitable means.For example, as discussed above, the particles may be loaded with anactive material by feeding an active compound to the extruder with thefirst aqueous solution comprising a surfactant. The active compound mayalso be added to the surface of the loaded particles. In embodiments,the ratio by weight of the at least one cosmetically or pharmaceuticallyactive compound to the weight of the porous particles may be from about1:1000 to about 10:1, such as about 1:100 to about 1:1.

Amounts of active compounds introduced into particles may depend on thedesired effect. In embodiments, the active compound or material, such asa cosmetic, a chemical and/or a pharmaceutical, may be present in theporous particles in an amount of active material ranging from about 1 to43% by weight, such as from about 2 to about 40% by weight, or fromabout 5 to about 30% by weight, relative to the total weight of theparticles once loaded.

FIG. 1 is a cross-section schematic diagram of an embodiment of acontinuous process for manufacturing porous nanoparticles. Embodimentsof the process use a screw extruder 5, shown as a multi-screw extruder,to which the resin and neutralizing agent mixture may be fed. Atwin-screw extruder may be used in various applications. For example, atwin screw extruder may provide types of mixing such as distributivemixing, dispersive mixing, dissipative mixing, chaotic mixing, andpumping. A twin screw extruder allows the resin and neutralizing agentto be co-fed into the twin screw extruder at a defined rate, to add asurfactant solution in a downstream portion of the extruder, to add afirst and second aqueous solution at further downstream portions of theextruder, and to emulsify the components in the extruder.

In FIG. 1, a dry-blended resin mixture of a resin and a neutralizingagent may be fed into the screw extruder 5 at a controlled rate througha hopper 25 by means of a gravimetric feeder (not shown). After beingfed into the screw extruder 5, the resin mixture passes through a feedsection I of the extruder 5. A first aqueous solution comprising asurfactant may be added through injection port N₀, forming awater-in-oil emulsion with the resin solution as it passes throughsection II of the extruder 5. A second aqueous solution comprisingdeionized water may be added through injection port N1, before theemulsion undergoes phase inversion, yielding a water-in-oil-in-waterdouble emulsion with nanoporous morphology as the emulsion passesthrough section III of the extruder 5. Deionized water may be addedthrough an injection port N3, to dilute the water-in-oil-in-water doubleemulsion and make it more freely flowing. The latex emulsion withnanoporous morphology having a desired particle size and a desired poresize emerges at the end 65 of the extruder 5 and may be analyzed foruniformity, pore size, and particle size.

The extruder 5 comprises a screw shaft that may be connected to a motor(not shown) through a gear box (not shown) to turn the screw. The screwspeed may be accurately controlled by the motor and the gear box. Abarrel (not shown) provides a housing for the screws. Both the barreland the screw may be segmented and each section may be heated at adesired temperature. Because the screw extruder 5 may be segmented andthe temperature of each section may be controlled independently at adesired temperature. For example, the multiple segments may each beheated to a temperature of from about 70° C. to about 200° C., such asfrom about 80° C. to about 180° C., or from about 85° C. to about 175°C. In embodiments, the segments may be heated to form a temperaturegradient. The ability to set different temperature profiles along thebarrel may allow for greater control of particle size and uniformity.

As discussed above, the resin and the neutralizing agent may be added tothe extruder through a hopper 25 in the feed section I of the extruder5. Prior to the feeding, the toner components may be dry-blended for aperiod of from about 5 minutes to about 60 minutes, such as from about10 minutes to about 50 minutes, or from about 15 minutes to about 45minutes. Alternatively, the resin and neutralizing agent may be co-fedindependently using separate gravimetric feeders, as the components willbecome well-mixed in the melting/metering region of the extruder.

A first aqueous solution comprising a surfactant and optionally anactive agent may be added at injection port N₀. The injection port N₀may be located downstream of a melting/metering region and upstream of adispersion region. To produce sufficient shearing to occur at thebarrel-wall of the extruder, the extruder may be fully filled in theinjection region. Local pressures may be dependent on the amount ofwater added, the temperature of the barrel, and the amount of surfactantused. In embodiments, the pressure may be from about 100 to about 1000psi. The feeding rate for an 18 mm extruder with 40 L/d may be fromabout 0.5 kg/hr to about 2.5 kg/hr. In embodiments, the screw speed maybe from about 100-600 RPM. In embodiments, the surfactant solution maybe pre-heated, such as to match the barrel temperature.

While FIG. 1 indicates that the resin and neutralizing agent are addedthrough the hopper 25 and the surfactant (and optionally active agent)are added through the injection port N₀, the neutralizing agent may beco-fed with the surfactant (and optionally an active agent) at otherlocations, such as at injection port N₀, or the resin, the neutralizingagent, and the surfactant (optionally with an active agent) may beco-fed through the hopper 25.

In embodiments, the first aqueous solution comprising a surfactant (andoptionally an active agent) may be mixed with the resin and neutralizingagent in the section II of the extruder 5, such that a water-in-oilemulsion is formed. Prior to phase inversion of the emulsion in sectionIII of the extruder 5, deionized water may be added through injectionport N1. For example, in embodiments, injection port N1 may be locateddirectly adjacent to injection port N₀ (if the first aqueous solutioncomprising surfactant is added through injection port N₀) or directlyadjacent to the hopper 25 (if the surfactant is added through the hopper25). In embodiments, the deionized water may be pre-heated, such as tothe barrel temperature, prior to injection to minimize temperature dropwithin the barrel of the extruder. A water-in-oil-in-water doubleemulsion may be produced as the mixture passes through section III ofthe extruder 5.

The mixture may then be continuously fed to a section IV of the extruder5, where deionized water may optionally be added through injection portN₂ to dilute the double emulsion and make it more flowable. Thedeionized water may be pre-heated, for example to the barreltemperature, prior to injection to minimize temperature drop within thebarrel of the extruder. In other embodiments, deionized water is notadded to the extruder after the formation of the double emulsion, andthe undiluted double emulsion may proceed directly to the pumping zone Vof the extruder for collection.

The double emulsion may then be pumped through the pumping zone V of theextruder 5 and collected from the end of the extruder, and porousnanoparticles may be continuously collected. In embodiments, the averageresidence time within the extruder may be in the range of from about 1minute to about 2 hours, such as in the range of from about 2 minutes toabout 30 minutes, or in the range of from about 4 minutes to about 10minutes.

If a second deionized water injection is not added in the extruder todilute the solution and make it more flowable, or if further dilution ofthe double emulsion is desired, the double emulsion may be collected,for example in a continuous stirred-tank reactor, and deionized watermay be added outside of the extruder. Porous nanoparticles may then becollected.

Resins

Any suitable resin may be utilized in the processes of the presentdisclosure. In embodiments, the resins may be an amorphous resin, acrystalline resin, and/or a combination thereof. In further embodiments,the resin may be a polyester resin, including the resins described inU.S. Pat. Nos. 6,593,049 and 6,756,176, the disclosures of each of whichare hereby incorporated by reference in their entireties. Suitableresins may also include a mixture of an amorphous polyester resin and acrystalline polyester resin as described in U.S. Pat. No. 6,830,860, thedisclosure of which is hereby incorporated by reference in its entirety.

In embodiments, the resin may be a polyester resin formed by reacting adiol with a diacid in the presence of an optional catalyst. For forminga crystalline polyester, suitable organic diols include aliphatic diolswith from about 2 to about 36 carbon atoms, such as 1,2-ethanediol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,2,2-dimethylpropane-1,3-diol, 1,6-hexanediol, 1,7-heptanediol,1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol andthe like including their structural isomers. The aliphatic diol may be,for example, selected in an amount of from about 40 to about 60 mol %,such as from about 42 to about 55 mol %, or from about 45 to about 53mol %, and a second diol can be selected in an amount of, for example,from about 0 to about 10 mol %, such as from about 1 to about 4 mol % ofthe resin.

Examples of organic diacids or diesters including vinyl diacids or vinyldiesters selected for the preparation of the crystalline resins includeoxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid,azelaic acid, sebacic acid, fumaric acid, dimethyl fumarate, dimethylitaconate, cis, 1,4-diacetoxy-2-butene, diethyl fumarate, diethylmaleate, phthalic acid, isophthalic acid, terephthalic acid,naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid,cyclohexane dicarboxylic acid, malonic acid and mesaconic acid, adiester or anhydride thereof. The organic diacid may be selected in anamount of, for example, from about 40 to about 60 mol %, such as fromabout 42 to about 52 mol %, or from about 45 to about 50 mol %, and asecond diacid can be selected in an amount of from about 0 to about 10mol % of the resin, such as from about 1 to about 9 mol % of the resin,or from about 2 to about 8 mol % of the resin.

Examples of crystalline resins include polyesters, polyamides,polyimides, polyolefins, polyethylene, polybutylene, polyisobutyrate,ethylene-propylene copolymers, ethylene-vinyl acetate copolymers,polypropylene, mixtures thereof, and the like. Specific crystallineresins may be polyester based, such as poly(ethylene-adipate),poly(propylene-adipate), poly(butylene-adipate),poly(pentylene-adipate), poly(hexylene-adipate), poly(octylene-adipate),poly(ethylene-succinate), polypropylene-succinate),poly(butylene-succinate), poly(pentylene-succinate),poly(hexylene-succinate), poly(octylene-succinate),poly(ethylene-sebacate), poly(propylene-sebacate),poly(butylene-sebacate), poly(pentylene-sebacate),poly(hexylene-sebacate), poly(octylene-sebacate),poly(decylene-sebacate), poly(decylene-decanoate),poly(ethylene-decanoate), poly(ethylene dodecanoate),poly(nonylene-sebacate), poly(nonylene-decanoate),copoly(ethylene-fumarate)-copoly(ethylene-sebacate),copoly(ethylene-fumarate)-copoly(ethylene-decanoate),copoly(ethylene-fumarate)-copoly (ethylene-dodecanoate),copoly(2,2-dimethylpropane-1,3-diol-decanoate)-copoly(nonylene-decanoate)-,poly(octylene-adipate). Examples of polyamides includepoly(ethylene-adipamide), poly(propylene-adipamide),poly(butylenes-adipamide), poly(pentylene-adipamide),poly(hexylene-adipamide), poly(octylene-adipamide),poly(ethylene-succinimide), and polypropylene-sebecamide). Examples ofpolyimides include poly(ethylene-adipimide), poly(propylene-adipimide),poly(butylene-adipimide), poly(pentylene-adipimide),poly(hexylene-adipimide), poly(octylene-adipimide),poly(ethylene-succinimide), poly(propylene-succinimide), andpoly(butylene-succinimide).

The crystalline resin may be present, for example, in an amount of fromabout 1 to about 50 percent by weight of the components, such as fromabout 3 percent to about 40 percent by weight of the components, or fromabout 5 to about 35 percent by weight of the components. The crystallineresin can possess various melting points of, for example, from about 30°C. to about 120° C., such as from about 40° C. to about 100° C., or fromabout 50° C. to about 90° C. The crystalline resin may have a numberaverage molecular weight (M_(N)), as measured by gel permeationchromatography (GPC) of, for example, from about 1,000 to about 50,000,such as from about 1,500 to about 40,000, or from about 2,000 to about25,000, and a weight average molecular weight (M_(W)) of, for example,from about 2,000 to about 100,000, such as from about 1,500 to about90,000, or from about 3,000 to about 80,000, as determined by GelPermeation Chromatography using polystyrene standards. Thepolydispersity index (M_(W)/M_(N)) of the crystalline resin may be anydesired value, such as, for example, a polydispersity index of fromabout 2 to about 6, such as from about 3 to about 4.

Examples of diacids or diesters including vinyl diacids or vinyldiesters utilized for the preparation of amorphous polyesters includedicarboxylic acids or diesters such as terephthalic acid, phthalic acid,isophthalic acid, fumaric acid, trimellitic acid, dimethyl fumarate,dimethyl itaconate, cis, 1,4-diacetoxy-2-butene, diethyl fumarate,diethyl maleate, maleic acid, succinic acid, itaconic acid, succinicacid, succinic anhydride, dodecylsuccinic acid, dodecylsuccinicanhydride, glutaric acid, glutaric anhydride, adipic acid, pimelic acid,suberic acid, azelaic acid, dodecanediacid, dimethyl terephthalate,diethyl terephthalate, dimethylisophthalate, diethylisophthalate,dimethylphthalate, phthalic anhydride, diethylphthalate, dimethylsuccinate, dimethylfumarate, dimethylmaleate, dimethylglutarate,dimethyladipate, dimethyl dodecylsuccinate, and combinations thereof Theorganic diacids or diesters may be present, for example, in an amountfrom about 40 to about 60 mol % of the resin, such as from about 42 toabout 52 mol % of the resin, or from about 45 to about 50 mol % of theresin.

Examples of diols which may be utilized in generating the amorphouspolyester include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol,1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol,2,2-dimethylpropanediol, 2,2,3-trimethylhexanediol, heptanediol,dodecanediol, bis(hydroxyethyl)-bisphenol A,bis(2-hydroxypropyl)-bisphenol A, 1,4-cyclohexanedimethanol,1,3-cyclohexanedimethanol, xylenedimethanol, cyclohexanediol, diethyleneglycol, bis(2-hydroxyethyl)oxide, dipropylene glycol, dibutylene, andcombinations thereof. The amount of organic diols selected can vary, andmay be present, for example, in an amount from about 40 to about 60 mol% of the resin, such as from about 42 to about 55 mol % of the resin, orfrom about 45 to about 53 mol % of the resin.

Polycondensation catalysts which may be utilized in forming either thecrystalline or amorphous polyesters include tetraalkyl titanates,dialkyltin oxides such as dibutyltin oxide, tetraalkyltins such asdibutyltin dilaurate, and dialkyltin oxide hydroxides such as butyltinoxide hydroxide, aluminum alkoxides, alkyl zinc, dialkyl zinc, zincoxide, stannous oxide, or combinations thereof. Such catalysts may beutilized in amounts of, for example, from about 0.01 to about 5 mol %,or from about 0.1 to about 4.5 mol %, or from about 0.5 to about 4 mol%, based on the starting diacid or diester used to generate thepolyester resin.

In embodiments, as noted above, an unsaturated amorphous polyester resinmay be utilized as a latex resin. Examples of such resins include thosedisclosed in U.S. Pat. No. 6,063,827, the disclosure of which is herebyincorporated by reference in its entirety. Exemplary unsaturatedamorphous polyester resins include poly(propoxylated bisphenolco-fumarate), poly(ethoxylated bisphenol co-fumarate),poly(butyloxylated bisphenol co-fumarate), poly(co-propoxylatedbisphenol co-ethoxylated bisphenol co-fumarate), poly(1,2-propylenefumarate), poly(propoxylated bisphenol co-maleate), poly(ethoxylatedbisphenol co-maleate), poly(butyloxylated bisphenol co-maleate),poly(co-propoxylated bisphenol co-ethoxylated bisphenol co-maleate),poly(1,2-propylene maleate), poly(propoxylated bisphenol co-itaconate),poly(ethoxylated bisphenol co-itaconate), poly(butyloxylated bisphenolco-itaconate), poly(co-propoxylated bisphenol co-ethoxylated bisphenolco-itaconate), poly(1,2-propylene itaconate), and combinations thereof.

In embodiments, a suitable amorphous polyester resin may be apoly(propoxylated bisphenol A co-fumarate) resin having the followingformula:

wherein m may be from about 5 to about 1000, such as from about 7 toabout 750, or from about 10 to about 500. Examples of such resins andprocesses for their production may include those disclosed in U.S. Pat.No. 6,063,827, the disclosure of which is hereby incorporated byreference in its entirety.

An example of a linear propoxylated bisphenol A fumarate resin which maybe utilized as a latex resin is available under the trade name SPARIIfrom Resana S/A Industrias Quimicas, Sao Paulo Brazil. Otherpropoxylated bisphenol A fumarate resins that may be utilized and arecommercially available include GTUF and FPESL-2 from Kao Corporation,Japan, and EM181635 from Reichhold, Research Triangle Park, N.C., andthe like.

Suitable crystalline resins may include those disclosed in U.S. PatentApplication Publication No. 2006/0222991, the disclosure of which ishereby incorporated by reference in its entirety. In embodiments, asuitable crystalline resin may be composed of ethylene glycol and amixture of dodecanedioic acid and fumaric acid co-monomers with thefollowing formula:

wherein b may be from about 5 to about 2000, such as from about 7 toabout 1750, or from about 10 to about 1500; and d may be from about 5 toabout 2000, such as from about 7 to about 1750, or from about 10 toabout 1500.

The amorphous resin may be present, for example, in an amount of fromabout 30 to about 90 percent by weight of the components, such as fromabout 35 to about 85 percent by weight of the components, or from about40 to about 80 percent by weight of the components. In embodiments, theamorphous resin or combination of amorphous resins utilized in the latexmay have a glass transition temperature of from about 30° C. to about80° C., such as from about 33° C. to about 85° C., or from about 35° C.to about 70° C. In further embodiments, the combined resins utilized inthe latex may have a melt viscosity of from about 10 to about 1,000,000PaS at about 130° C., such as from about 25 to about 500,000, or fromabout 50 to about 100,000 PaS.

One, two, or more resins may be used. In embodiments, where two or moreresins are used, the resins may be in any suitable ratio (e.g., weightratio) such as for instance of from about 1% (first resin)/99% (secondresin) to about 99% (first resin)/1% (second resin), such as from about10% (first resin)/90% (second resin) to about 90% (first resin)/10%(second resin). Where the resin includes an amorphous resin and acrystalline resin, the weight ratio of the two resins may be from about99% (amorphous resin):1% (crystalline resin), to about 1% (amorphousresin):90% (crystalline resin).

In embodiments the resin may possess acid groups which, in embodiments,may be present at the terminal of the resin. Acid groups which may bepresent include carboxylic acid groups, and the like. The number ofcarboxylic acid groups may be controlled by adjusting the materialsutilized to form the resin and reaction conditions.

In embodiments, the resin may be a polyester resin having an acid numberfrom about 2 mg KOH/g of resin to about 200 mg KOH/g of resin, inembodiments from about 5 mg KOH/g of resin to about 50 mg KOH/g ofresin. The acid containing resin may be dissolved in tetrahydrofuransolution. The acid number may be detected by titration with KOH/methanolsolution containing phenolphthalein as the indicator. The acid numbermay then be calculated based on the equivalent amount of KOH/methanolrequired to neutralize all the acid groups on the resin identified asthe end point of the titration.

Neutralizing Agent

In embodiments, the resin may be pre-blended with a weak base orneutralizing agent. In embodiments the base may be a solid, which avoidsthe risks and difficulties associated with pumping of a solution.

In embodiments, the resin and the neutralizing agent may besimultaneously fed through a co-feeding process, which may accuratelycontrol the feed rate of both the base and the resin into the extruderthroughout the process. Utilizing this process allows for control of thebase concentration and a more efficient process. Co-feeding may allowfor process repeatability and stability, and significantly lower initialstart-up waste.

In embodiments, the neutralizing agent may be used to neutralize acidgroups in the resins, so a neutralizing agent herein may also bereferred to as a “basic neutralization agent.” Any suitable basicneutralization reagent may be used in accordance with the presentdisclosure. In embodiments, suitable basic neutralization agents mayinclude both inorganic basic neutralization agents and organic basicneutralization agents. Suitable basic neutralization agents may includeammonium hydroxide, potassium hydroxide, sodium hydroxide, sodiumcarbonate, sodium bicarbonate, lithium hydroxide, potassium carbonate,combinations thereof, and the like. Suitable basic neutralization agentsmay also include monocyclic compounds and polycyclic compounds having atleast one nitrogen atom, such as, for example, secondary amines, whichinclude aziridines, azetidines, piperazines, piperidines, pyridines,bipyridines, terpyridines, dihydropyridines, morpholines,N-alkylmorpholines, 1,4-diazabicyclo[2.2.2]octanes,1,8-diazabicycloundecanes, 1,8-diazabicycloundecenes, dimethylatedpentylamines, trimethylated pentyl amines, pyrimidines, pyrroles,pyrrolidines, pyrrolidinones, indoles, indolines, indanones,benzindazones, imidazoles, benzimidazoles, imidazolones, imidazolines,oxazoles, isoxazoles, oxazolines, oxadiazoles, thiadiazoles, carbazoles,quinolines, isoquinolines, naphthyridines, triazines, triazoles,tetrazoles, pyrazoles, pyrazolines, and combinations thereof. Inembodiments, the monocyclic and polycyclic compounds may beunsubstituted or substituted at any carbon position on the ring.Monocyclic and polycyclic compounds may be substituted by replacinghydrogen atoms with one or more functional groups to form monocyclic andpolycyclic derivative compounds. The term “functional group” refers, forexample, to a group of atoms arranged in a way that determines thechemical properties of the group and the molecule to which it isattached. Examples of functional groups include halogen atoms, hydroxylgroups, carboxylic acid groups, and the like. The term “derivative”refers, for example, to a compound derived from another.

The basic neutralization agent may be utilized as a solid such as, forexample, sodium hydroxide powder, so that it is present in an amount offrom about 0.001% by weight to about 50% by weight of the resin, such asfrom about 0.01% by weight to about 25% by weight of the resin, or fromabout 0.1% by weight to about 5% by weight of the resin.

As noted above, the basic neutralization agent may be added to a resinpossessing acid groups. The addition of the basic neutralization agentmay thus raise the pH of an emulsion including a resin possessing acidgroups from about 5 to about 12, such as from about 6 to about 11, orfrom about 5 to about 10. The neutralization of the acid groups may, inembodiments, enhance formation of the emulsion.

Surfactants

In embodiments, the process of the present disclosure includes adding asurfactant during extrusion of the resin. Where utilized, a resinemulsion may include one, two, or more surfactants. The surfactants maybe selected from ionic surfactants and nonionic surfactants. Anionicsurfactants and cationic surfactants are encompassed by the term “ionicsurfactants.” In embodiments, the surfactant may be added as a solution,such as an aqueous solution, with a concentration from about 5% to about100% (pure surfactant) by weight, or from about 30% to about 95% byweight. In embodiments, the surfactant may be utilized so that it ispresent in an amount of from about 0.01% to about 20% by weight of theresin, such as from about 0.1% to about 10% by weight of the resin, orfrom about 1% to about 8% by weight of the resin.

Examples of nonionic surfactants that can be utilized for the processesillustrated herein and that may be included in the emulsion are, forexample, polyacrylic acid, methalose, methyl cellulose, ethyl cellulose,propyl cellulose, hydroxy ethyl cellulose, carboxy methyl cellulose,polyoxyethylene cetyl ether, polyoxyethylene lauryl ether,polyoxyethylene octyl ether, polyoxyethylene octylphenyl ether,polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate,polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether,dialkylphenoxy poly(ethyleneoxy) ethanol, available from Rhone-Poulencas IGEPAL CA-210™, IGEPAL CA-520™, IGEPAL CA-720™, IGEPAL CO-890™,IGEPAL CO-720™, IGEPAL CO-290™, IGEPAL CA-210™, ANTAROX 890™ and ANTAROX897™. Other examples of suitable nonionic surfactants include a blockcopolymer of polyethylene oxide and polypropylene oxide, including thosecommercially available as SYNPERONIC PE/F, in embodiments SYNPERONICPE/F 108.

Anionic surfactants which may be utilized include sulfates andsulfonates, sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkylsulfates and sulfonates, acids such as abitic acid available fromAldrich, NEOGEN R™, NEOGEN SC™ obtained from Daiichi Kogyo Seiyaku,combinations thereof, and the like. Other suitable anionic surfactantsinclude, in embodiments, DOWFAX™ 2A1, an alkyldiphenyloxide disulfonatefrom The Dow Chemical Company, and/or TAYCA POWER BN2060 from TaycaCorporation (Japan), which are branched sodium dodecyl benzenesulfonates. Combinations of these surfactants and any of the foregoinganionic surfactants may be utilized in embodiments.

Examples of the cationic surfactants, which are usually positivelycharged, include, for example, alkylbenzyl dimethyl ammonium chloride,dialkyl benzenealkyl ammonium chloride, lauryl trimethyl ammoniumchloride, alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethylammonium bromide, benzalkonium chloride, cetyl pyridinium bromide, C₁₂,C₁₅, C₁₇ trimethyl ammonium bromides, halide salts of quaternizedpolyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride,MIRAPOL™ and ALKAQUAT™, available from Alkaril Chemical Company,SANIZOL™ (benzalkonium chloride), available from Kao Chemicals, and thelike, and mixtures thereof.

EXAMPLES Example 1

Preparation of a sub-micron sized latex emulsion with nanoporousmorphology formed from an amorphous polyester resin.

100 parts of an amorphous polyester resin were blended with 1 partsodium hydroxide powder. The mixture was added to the hopper of agravimetric feeder and fed at a rate of 1.25 kg/hour to the feedingthroat in zone 0 of a twin-screw extruder having seven heated zones plusa heated die for a total of eight heated zones and one cooled feedingzone. The temperatures of the eight heated zones of the twin-screwextruder are summarized in Table 1. The screw speed of the extruder wasset to 300 RPM. In zone 2 of the screw extruder, an aqueous surfactantsolution comprising 47% DOWFAX 2A1 was injected at a rate of 2.89mL/min. In zone 3 of the twin-screw extruder, deionized water wasinjected at a rate of 4.44 mL/min. In zone 6 of the twin-screw extruder,deionized water was injected at a rate of 24.97 mL/min. Porousnanoparticles were collected after being discharged from the extruder.The process conditions of Example 1 are summarized in Table 1. SEMimages of a representative sample of the porous nanoparticles producedin Example 1 are shown in FIG. 2A (at ×40.0 k magnification) and FIG. 2B(at ×60 k magnification).

Example 2

Preparation of a sub-micron sized latex emulsion with nanoporousmorphology. 100 parts of an amorphous polyester resin were blended with1 part sodium hydroxide powder. The mixture was added to the hopper of agravimetric feeder and fed at a rate of 1.25 kg/hr to the feeding throatin zone 0 of a twin-screw extruder having seven heated zones plus aheated die for a total of eight heated zones and one cooled feedingzone. The temperatures of the eight heated zones of the twin-screwextruder are summarized in Table 1. The screw speed of the extruder wasset to 300 RPM. In zone 2 of the twin-screw extruder, an aqueoussurfactant solution comprising 47% DOWFAX 2A1 was injected at a rate of2.89 mL/min. In zone 3 of the twin-screw extruder, deionized water wasinjected at a rate of 6.51 mL/min. In zone 6 of the twin-screw extruder,deionized water was injected at a rate of 50.00 mL/min. Porousnanoparticles were collected after being discharged from the extruder.The process conditions of Example 2 are summarized in Table 1. SEMimages of a representative sample of the porous nanoparticles producedin Example 2 are shown in FIG. 3A (at ×20 k magnification) and FIG. 3B(at ×10.0 k magnification).

As discussed above, the morphology of the porous nanoparticles may becontrolled by adjusting the injection rate of the second aqueoussolution comprising deionized water. For example, of a representativesample of such porous nanoparticles are shown in FIG. 3A and FIG. 3B,where the surface porosity was created (in a process similar to thatemployed in Example 2) by increasing the injection rate of the secondaqueous solution comprising deionized water at N1 (see FIG. 1).

TABLE 1 Example 2 process conditions. Resin (1 ppH Surfactant Z₃ DIW Z₆DIW Zone Temperature (° C.) Example NaOH) [N0] [N1] [N2] RPM Z1 Z2 Z3 Z4Z5 Z6 Z7 Z8 1 1.25 kg/h 2.89 mL/min 4.44 mL/min 24.97 mL/min 300 160 170150 130 110 110 90 90 2 1.25 kg/h 2.89 mL/min 6.51 mL/min 50.00 mL/min300 160 170 150 130 110 100 90 90

Example 3

Preparation of a sub-micron sized latex emulsion with nanoporousmorphology formed from an amorphous polyester resin. 100 parts of anamorphous polyester resin were blended with 1 part sodium hydroxidepowder. The mixture was added to the hopper of a gravimetric feeder andfed at a rate of 1.25 kg/hour to the feeding throat in zone 0 of atwin-screw extruder having seven heated zones plus a heated die for atotal of eight heated zones and one cooled feeding zone. Thetemperatures of the eight heated zones of the twin-screw extruder aresummarized in Table 2. The screw speed of the extruder was set to 200RPM. In zone 2 of the screw extruder, an aqueous surfactant solutioncomprising 21% DOWFAX 2A1 was injected at a rate of 6 mL/min. In zone 3of the twin-screw extruder, an aqueous surfactant solution comprising21% DOWFAX 2A1 was injected at a rate of 3 mL/min. In zone 6 of thetwin-screw extruder, deionized water was injected at a rate of 38.43mL/min. Porous nanoparticles were collected after being discharged fromthe extruder. The process conditions of Example 3 are summarized inTable 2. SEM images of a representative sample of the porousnanoparticles produced in Example 3 are shown in FIG. 4A (at ×20 kmagnification) and FIG. 4B (at ×10.0 k magnification).

Example 4

Preparation of a sub-micron sized latex emulsion with nanoporousmorphology formed from an amorphous polyester resin. 100 parts of anamorphous polyester resin were blended with 1 part sodium hydroxidepowder. The mixture was added to the hopper of a gravimetric feeder andfed at a rate of 1.25 kg/hour to the feeding throat in zone 0 of atwin-screw extruder having seven heated zones plus a heated die for atotal of eight heated zones and one cooled feeding zone. Thetemperatures of the eight heated zones of the twin-screw extruder aresummarized in Table 2. The screw speed of the extruder was set to 200RPM. In zone 2 of the screw extruder, an aqueous surfactant solutioncomprising 21% DOWFAX 2A1 was injected at a rate of 8 mL/min. In zone 3of the twin-screw extruder, an aqueous surfactant solution comprising21% DOWFAX 2A1 was injected at a rate of 1 mL/min. In zone 6 of thetwin-screw extruder, deionized water was injected at a rate of 38.43mL/min. Porous nanoparticles were collected after being discharged fromthe extruder. The process conditions of Example 4 are summarized inTable 2. SEM images of a representative sample of the porousnanoparticles produced in Example 4 are shown in FIG. 5A (at ×20 kmagnification) and FIG. 5B (at ×10 k magnification).

TABLE 2 Example 4 process conditions. Resin Z₂ 21% Z₃ 21% Z₆ (1 ppHDOWFAX DOWFAX DIW Zone Temperature (° C.) Example NaOH) 2A1 [N0] 2A1[N1] [N2] RPM Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 3 1.25 kg/h 6 mL/min 3 mL/min38.43 200 160 165 135 115 95 95 95 125 4 1.25 kg/h 8 mL/min 1 mL/min38.43 200 160 165 135 115 95 95 95 125

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art, and are also intended to beencompassed by the following claims.

What is claimed is:
 1. Porous nanoparticles comprising: a resincomposition comprising at least one polyester resin in the absence of anorganic solvent, and a surfactant; wherein the porous nanoparticles havea particle size of from about 50 nm to about 2 μm, a pore diameter offrom about 20 nm to about 400 nm, and a surface porosity of from about10% to 60% of the surface of the porous nanoparticles.
 2. The porousnanoparticles according to claim 1, wherein the porous nanoparticleshave cell walls with a cell wall thickness of from about 5 nm to about100 nm.
 3. The porous nanoparticles according to claim 1, wherein the atleast one polyester resin is selected from the group consisting ofamorphous resins, crystalline resins, and combinations thereof.
 4. Theporous nanoparticles according to claim 3, wherein the at least onepolyester resin comprises an amorphous resin.
 5. The porousnanoparticles according to claim 1, wherein the porous nanoparticlescomprise pores loaded with at least one active compound selected fromthe group consisting of a cosmetic compound, a chemical compound and apharmaceutical compound.
 6. The porous nanoparticles according to claim1, wherein the ratio by weight of the at least one active compound tothe weight of the porous nanoparticles is from about 1:1000 to about10:1.
 7. The porous nanoparticles according to claim 1, wherein the atleast one active compound is present in the porous nanoparticles in anamount of from about 1 to 43% by weight relative to the total weight ofthe porous nanoparticles once loaded.
 8. The porous nanoparticlesaccording to claim 1, wherein the surfactant is present in an amount offrom about 0.01% to about 20% by weight of the resin composition. 9.Porous nanoparticles comprising: a resin composition comprising at leastone polyester resin in the absence of an organic solvent, and asurfactant; wherein the porous nanoparticles have a particle size offrom about 75 nm to about 1 μm, a pore diameter of from about 25 nm toabout 180 nm, and a surface porosity of from about 10% to 60% of thesurface of the porous nanoparticles.
 10. The porous nanoparticlesaccording to claim 9, wherein the porous nanoparticles have cell wallswith a cell wall thickness of from about 10 nm to about 50 nm. 11.Porous nanoparticles comprising: a resin composition comprising at leastone polyester resin in the absence of an organic solvent, and asurfactant; wherein the porous nanoparticles have a particle size offrom about 50 nm to about 2 μm and a pore diameter of from about 20 nmto about 400 nm, and a surface porosity of from about 10% to 60% of thesurface of the porous nanoparticles; wherein the porous nanoparticlesare produced by a process comprising: adding a first aqueous solutioncomprising a surfactant to the resin composition comprising at least oneresin to form a water-in-oil emulsion; adding a second aqueous solutioncomprising deionized water to the water-in-oil emulsion prior to phaseinversion to form a water-in-oil-in-water double emulsion comprisingporous nanoparticles; and recovering porous nanoparticles from thedouble emulsion.
 12. The porous nanoparticles according to claim 11,wherein the resin composition further comprises a neutralizing agent.13. The porous nanoparticles according to claim 12, wherein theneutralizing agent is sodium hydroxide.
 14. The porous nanoparticlesaccording to claim 12, wherein the neutralizing agent is present in anamount of from about 0.001% by weight to about 50% by weight of theresin composition.
 15. The porous nanoparticles according to claim 11,further comprising adding deionized water after formation of the doubleemulsion.
 16. The porous nanoparticles according to claim 11, whereinthe first aqueous solution comprising a surfactant further comprises atleast one active compound selected from the group consisting of acosmetic compound, a chemical compound and a pharmaceutical compound.17. The porous nanoparticles according to claim 11, wherein the firstaqueous solution comprising a surfactant is fed at a rate such that thesurfactant is at a concentration of from about 2% by weight to about 15%by weight of the resin.
 18. The porous nanoparticles according to claim11, wherein the second aqueous solution further comprises a surfactant.19. The porous nanoparticles according to claim 11, wherein the porousnanoparticles have cell walls with a cell wall thickness of from about 5nm to about 100 nm.
 20. The porous nanoparticles according to claim 11,wherein the at least one polyester resin is selected from the groupconsisting of amorphous resins, crystalline resins, and combinationsthereof.